Professional Quality Psychrometric Calculator

Calculate Thermodynamic Properties of Moist (Humid) Air

 Thermodynamic Properties of Moist (Humid) Air

The site provides a feature rich, professional quality Psychrometric Calculator web application.

The HumidAirWeb application calculates 35 thermodynamic properties of humid (moist) air. It allows 21 different combinations of input variables to be used for calculations.

Input variables that can be used are:

  • Pressure
  • Dry bulb temperature
  • Wet bulb temperature
  • Dew point temperature
  • Relative humidity
  • Humidity ratio
  • Enthalpy
  • Entropy
  • Volume

 Used Formulations

The "Psychrometric Calculator" is based on the formulations developed by Hyland and Wexler. These formulations are approved by ASHRAE as documented in the 1997 ASHRAE Handbook "Fundamentals". Hyland and Wexler presented the equation of state in:

  • Formulations for the thermodynamic properties of the saturated phases of H2O from 173.15 K to 473.15 K, W. Hyland and A.Wexler, ASHRAE Transactions, 89(2A) 500-519, 1983.
  • Formulations for the thermodynamic properties of dry air from 173.15 K to 473.15 K, and of saturated moist air from 173.15 K to 372.15 K, at pressures to 5 MPa, R. W. Hyland and A. Wexler, ASHRAE Transactions, 89(2A) 520-535, 1983.


There are two packages available:
  • The Basic package is free and doesn't require registration.
  • For the Premium package, registration is valid for 5 months (150 days) and it will not be extended automatically. After 5 months if you wish to continue using the application you will have to register and create a new account again.

The Registration includes free technical support for the duration of the subscription.

Rent-To-Own program   NEW

The value of each subscription you purchase (1 or more) can be applied as a discount towards a purchase of the full license of our related HumidAir (Psychrometrics) desktop software (HumidAir Excel Add-In or HumidAir Desktop Application). This also applies retroactively for all subscriptions since the beginning of 2019.

Save all subscription order IDs. When you wish to apply this discount towards a purchase of the full license on any of the mentioned desktop software send us an email and we will provide the steps to complete the purchase of the full license with the discount applied.

If you have any questions, please don't hesitate to contact sales. Contact information is provided on the following page:
 Contact Us - (opens in a new tab).


Basic Package

$0.00 Free

This is a free service.
Free Psychrometric Calculator online.

  • Calculate thermodynamic properties based on dry bulb temperature, relative humidity and pressure at 1 bar or 14.5 psi.
  • Save data to Excel,
    CSV or Open Office File Format.
This free service is available only on the Weekends (Saturdays and Sundays).
You don't need account for the Basic Package.

Premium Package

$29.95 (150 Days)

This is a 5 months subscription fee for using the HumidAir Web (Psychrometric Calculator) online.

  • No limitations for calculation of thermodynamic properties.
  • Heating / Cooling process calculations.
  • Mixing stream calculations.
  • Save data to Excel,
    CSV or Open Office File Format.

 User Settings

The following user settings, from the last session, are automatically restored:

  • Units
  • Theme
  • Setup Panel visibility
  • Output Panel visibility
  • Registered users can select a new option during Login process, to be automatically logged-in in the future

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